Replace existing Unico? Or change to mini-splits?

carlkevanston

I'm in an older (1950's) tri-level. Over 20 years ago, added a floor with 2 large bedrooms and bath. Changed to HW baseboard heat at the time so I chose a high-velocity Unico for A/C. Chicago area, so cooling is a relatively short season. Overall, system has performed well. Blower motor burned up a capacitor during our recent heat wave and technician said my R-22 is a little low, so, probably a leak somewhere. Reading about newer R-410A systems, it seems I would need to add additional air outlets in existing rooms - not an easy task given my construction. Tech also said my 20-year old fiberglass trunk is showing some deterioration. Reading up on fiberglass duct life expectancy, I see that some flaking of the fiberglass is pretty normal. Quote for a new air trunk, new air handler and new 4-ton A/C was out of sight!

I could easily put in a 2-head mini-split for the top floor and have much better temperature regulation. Question is, what to do about the other 7 rooms on lower levels? Do I replace the fiberglass trunk with an insulated metal duct and put in a much smaller system? With mini-splits on the top floor, I'd only need to cool about 1100 sq. ft. I'll have to run the heat loss numbers, but probably a 2.5 ton system would be sufficient.

And then there is the question of refrigerant? EPA has some new rules already for next year about R-410A. Am I just patching with a system that will be outdated in 5 years? Should I look at putting in a mini-split style system for all 10 rooms (including 2 small bathrooms)? The room-by-room control would be great, but I'd probably have to go with at least a few cassette units for a couple of the rooms and running the refrigerant lines for at least 3 of the rooms would be more difficult.

My existing HVAC contractor basically just presented the R&R option to a newer R-410A system using the existing 2.5" ducts. After reading material from the Unico site and others, as well as posts here, it sounds like their solution is NOT the right way to handle this.

Fortunately, the system is cooling OK after the capacitor replacement. Given that it is already September, I think I can research this and wait till March or April to handle the replacement.

Thank you for all suggestions and comments.

Jamie Hall

Your old system used R-22? Just recharging it may cost as much as a whole new system. R-410A is also being phased out, and the newer refrigerant is — surprise — more costly, but doesn't require quite as much change in the actual hardware.

That said, the changes in refrigerants shouldn't require new air ducting or outlets, provided the old ones were satisfactory. What it will require is changes in the evaporator and condensors and compressors in other words, the entire mechanical guts of the system.

pecmsg

https://forum.heatinghelp.com/discussion/comment/1809244#Comment_1809244

Along with leak detecting system(s).

pecmsg

if it’s a little low then there is a leak. Find the leak then make the decision to

Repair

or

Replace.

I like minis, they have there place for spot cooling / heating but not for multiple rooms.